The Department of Immunology and Infectious Diseases (DIID) in the Division of Biologic Sciences (DBS) at the Harvard School of Public Health comprises a team of scientists who work on problems related to the immune response and to the biology, epidemiology and immunology of infectious diseases. The Division of Biological Science (DBS), established in 1993, is an umbrella structure that encompasses the biologic laboratory sciences in the areas of Immunology and Infectious Diseases. Cancer Cell Biology, Environmental Health, and Nutrition at the Harvard School of Public Health. The Ph.D. Program in Biological Sciences in Public Health (BPH) is located at the Harvard School of Public Health and is offered by the Faculty of Arts and Sciences of the Graduate School of Arts and Sciences. This predoctoral training grant application would support BPH students who choose to work in laboratories of faculty members of the Department of Immunology and Infectious Diseases. The BPH program provides an opportunity for training a cadre of investigators who, while possessing expertise in the individual fields of biological research, also possess a broad interdisciplinary knowledge of epidemiology and biostatistics. It has become increasingly evident that progress in disease prevention is optimally promoted by a close interaction between epidemiologis- ts and laboratory scientists, where laboratory discoveries and epidemio- logical observations interact in an iterative manner to advance research in both fields. Furthermore, basic biological and epidemiological discoveries must be placed in a wide social context. This program encourages active collaboration among scientists who share complementary interests in developing closer linkages between laboratory research and field work-all with an eye to developing innovative approaches to prevention.